General methods to retard or prevent oxidation of foods are an addition of antioxidant or a substitution of air in pouches with inactive gases, for instance nitrogen or carbon dioxide or an addition of oxygen absorbing agents into pouches. As for nuts, an addition of antioxidants is not so effective. And a substitution of air with an inactive gas or an addition of oxygen absorbing agents in pouches need much cost, because more precious pouch material is required to cut off an invasion of oxygen across pouch films, and these methods lose their effect after opening pouches. It has never been known to treat nuts with compressed carbon dioxide gas to retard their oxidation, so this is a novel method of antioxidation and devices of this invention are also novel.